Current treatment for HIV infection is aimed at suppressing the virus (HIV) and managing the symptoms and complications that accompany this infection. The body's immune system (natural defense) is believed to be important in controlling the activity of HIV. Interleukin-10 (IL-10) is a protein substance made by the body's immune system that may affect immune function. IL-10 has been shown to induce a transient and mild decrease of HIV in the blood. For this reason, IL-10 may be of use in the treatment of HIV infection, especially when antiviral drugs alone do not completely suppress HIV replication. The primary purpose of this study is to evaluate the safety and activity of multiple doses of SCH 52000 on suppression of viremia (virus in the blood) in persons with HIV infection and CD4 counts less than 50 and to define the time course and duration of the resonse. Secondary goals are to determine the effect of the drug on various lymphocyte (immune cell) functions.